Had a few too many? A laser is waiting for you.

“Don’t drink and drive.” You’ve heard it before, and you’ll hear it again. But some people still refuse to abide by that rule. It’s likely that you’ve shared the road with dozens of drunken drivers over your lifetime, and the numbers prove it: In the U.S., more than 4 million adults have admitted to driving under the influence of alcohol at least once in 2010, yielding an estimated 112 million alcohol-impaired episodes in just that year alone. The European Union had more than 5600 people killed in 2012 due to drunken driving – 46 percent of its 12,000 total traffic fatalities. These numbers are concerning enough, but they might even be low estimates because of underreporting and a lack of enforcement. Drunken driving continues to be a pervasive, preventable problem, with police suspicion being its only resistance – that is, until now.

Photonics has entered the field with an intelligent laser system that can detect alcohol vapors in moving cars, even before an officer has pulled over the vehicle. Developed at the Polish Military University of Technology’s Institute of Optoelectronics, the new laser device uses standoff detection as a way to identify chemical and biological compounds.

“We all are already familiar with laser instruments used by the police for speed-limit enforcement,” said Dr. Marco Gianinetto, a professor at the Polytechnic University of Milan and associate editor of the Journal of Applied Remote Sensing, where the research was published. “Now, these researchers have demonstrated how a laser device could be effectively used for detecting drunken drivers and thereby helping to reduce the number of accidents caused by drivers under the influence of alcohol.”

Courtesy of the Journal of Applied Remote Sensing.
A monitoring laser beam set up on one side of the road is directed toward a reflective mirror on the other side. The beam is modulated by a chopper to make synchronous detection possible when a car passes through the beam. Dichroic and spherical mirrors direct the monitoring laser beam, along with a second beam from a pilot laser. Signals from two detectors are analyzed by a specially developed electronic system, and an oscilloscope accurately adjusts the entire system.

Since alcohol vapor comes from the human lungs, scientists had to simulate the breath of a drunken driver inside the car by evaporating a mixture of water and alcohol at the correct concentration and temperature. The results showed that the presence of alcohol vapors was detected by the laser system when a human being has a blood alcohol concentration of 0.1 percent or higher. If detected, a notification is sent to a police officer waiting down the road, along with a photo of the vehicle and its license plate. The officer can then stop the car and use conventional tests to determine whether the driver is intoxicated.

The researchers note various counter-measures that could be used against the technology, such as driving with the windows open, applying solar screens on the side windows or even using air conditioning. However, they say such situations are “very easily detected by the system,” which could send this information to a police officer, notifying him that the vehicle should be checked. Other issues, such as identifying the breath of a drunken passenger instead of the driver, or picking up vapor from spilled alcohol, are possible. But the device, investigators say, will “surely decrease the number of cars that have to be checked by police” in situations such as sobriety checkpoints and will increase the efficiency of police stops.

alcohol is not always the reason for accidents. A good driver and experienced alcoholist, even with "a few glasses too many", may still drive better than a lady with a distracting child on the passenger seat.